In 1875,Charles Darwin reported on a family group living in what is now Pakistan that had a condition known as ectodermal dysplasia,which results in few teeth and inactive sweat glands.Darwin wrote that "…no instance has occurred of a daughter being affected...though the daughters in the above family are never affected,they transmit the tendency to their sons: and no case has occurred of a son transmitting it to his sons.The affection thus appears only in alternate generations,or after long intervals." The most likely explanation of Darwin's observations is that ectodermal dysplasia
A) results from spontaneous mutations.
B) is a sex-linked condition.
C) results from x-inactivation.
D) probably has environmental,as opposed to genetic causes.

Question

Quizplus · Accepted Answer

Darwin's observation that the condition only appears in alternate generations suggests that it is inherited in a sex-linked manner. This means that sons inherit the genetic mutation from their mothers, who are carriers of the condition but are unaffected themselves. Daughters, on the other hand, would need to inherit the mutated gene from both parents to be affected, which is a much rarer occurrence.

In 1875,Charles Darwin Reported on a Family Group Living in What